Systems and methods for preparing a proximal tibia

ABSTRACT

A method of preparing a tibia to receive a tibial implant component includes performing a first set of cuts to prepare a floor interface surface on the tibia, wherein the floor interface surface includes a portion on each side of a tibial eminence extending above the floor interface surface on the tibia. The method further includes performing a second set of cuts to prepare a tibial eminence wall interface surface, wherein the wall interface surface extends substantially perpendicular to the floor interface surface between the floor interface surface and a top surface of the tibial eminence. The method further includes performing a third set of cuts to prepare a radiused intersection between the floor interface surface and the wall interface surface. The sets of cuts are performed subject to a cutting restraint guide. At least one set of cuts may be performed using a rotary cutter.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/579,730, filed Dec. 22, 2014, which claims the benefit of andpriority to U.S. Provisional Patent Application Ser. No. 61/922,723,filed Dec. 31, 2013, the disclosures of which are hereby incorporated byreference in their entireties.

BACKGROUND

The present disclosure relates generally to systems and methods forperforming resection of bone, and more particularly to systems andmethods for preparing the proximal tibia to receive a tibial prostheticimplant component.

The knee joint comprises the interface between the distal end of thefemur and the proximal end of the tibia. In a properly-functioning kneejoint, medial and lateral condyles of the femur pivot smoothly alongmenisci attached to respective medial and lateral condyles of the tibia.When the knee joint is damaged, the natural bones and cartilage thatform the joint may be unable to properly articulate, which can lead tojoint pain and, in some cases, interfere with normal use of the joint

In some situations, surgery is required to restore normal use of thejoint and reduce pain. Depending upon the severity of the damage, thesurgery may involve partially or completely replacing the joint withprosthetic components. During such knee replacement procedures, asurgeon resects damaged portions of the bone and cartilage, whileattempting to leave healthy tissue intact. The surgeon then fits thehealthy tissue with artificial prosthetic components designed toreplicate the resected tissue and restore proper knee joint operation.

One knee replacement procedure—total knee arthroplasty (“TKA”)—involvesthe resection of some or all of each of the medial and lateral condylesof both the femur and tibia and the removal of the fibro-cartilagemenisci located at the femorotibial interface. A prosthetic femoralcomponent, typically made of cobalt-chromium alloy or other strong,surgical-grade metal, is fitted and secured to the distal end of thefemur to replace the resected portion of the femur. Similarly, aprosthetic tibial component, the base of which is also typically made ofcobalt-chromium alloy, titanium, or other suitable metal, is fitted andsecured to the proximal end of the tibia to replace the resected portionof the tibia.

In some situations, the patient's bone at the knee joint may havedeteriorated to a point which requires TKA surgery, but one or more ofthe patient's cruciate ligaments (e.g., the anterior cruciate ligament(ACL) and/or posterior cruciate ligament (PCL)) are in sufficientcondition to provide adequate joint stability. Maintaining the nativecruciate ligaments is often advantageous, as doing so is generallythought to aid in proprioception (the ability to sense where parts ofthe body are in relation to each other) and could make activities likeclimbing stairs feel more stable or natural. Preserving the cruciateligaments can also promote more normal front to back knee motion, whichcan enhance the patient's ability to maintain preoperative range ofmotion, particularly as it relates to deep flexion. The ligaments alsoaid in joint stability.

Each of the native cruciate ligaments connects to one of the femoralcondyles, passes within the intercondylar region of the femur, andconnects to the center-top portion of the tibia called the tibialeminence. In order to accommodate the passage of the cruciate ligaments,the femoral and tibial implant components used in cruciate-retainingprocedures typically comprise intercondylar cutaways that define avertical passage between the intercondylar fossa of the femur and thetibial eminence. The medial and lateral components of each of thefemoral and tibial prosthetic components are separated by a deepintercondylar passage (or “notch”) that allows for passage of cruciateligaments vertically through the notch.

During normal operation of the knee joint, the cruciate ligaments canexert significant tension at the attachment site of the tibia called thetibial eminence. In a healthy knee joint, there is sufficient tissuesurrounding the tibial eminence to aid in the distribution of this forceacross the surface of the tibia. Installation of a cruciate-retainingtibial prosthetic component, while aimed at preserving an attachmentsite at the tibial eminence, typically requires significant removal ofthe surrounding native tissue of the tibia to make way for installationof the tibial implant. This surrounding tissue provides much of theattachment strength that counteracts the tension applied by the cruciateligaments, and removal of this tissue can weaken the attachment strengthof the tibial eminence.

Present methods of tibial preparation (i.e. removal of bone to receivethe tibial implant) can result in inadvertent removal of even moretissue than is necessary for installation of the tibial implant, whichfurther weakens the strength of the tibial eminence and can result inimplant failure. In particular, present methods employ manualoscillating sagittal saws to make planar cuts. Manual saws makinghorizontal cuts can overcut into the eminence, and manual saws makingvertical cuts can cut too deep into the tibial bone. These overcutsweaken the tibial eminence and the cruciate ligament attachment.Additionally, traditional planar saws can create sharp corners and highstress risers, which puts additional stress at the tibial eminence.Attempts to improve the undercut problem, particularly at the lateralovercuts, and reduce stress risers, have led to adding drilled pinsplaced at the intersection of the resected portion and the remainingtibial eminence portion to stop overcutting. However, saw blades oftenskive and can still result in overcutting and stress risers.

SUMMARY

One embodiment of the invention relates to a method of preparing a tibiato receive a tibial implant component. The method includes performing afirst set of cuts to prepare a floor interface surface on the tibia,wherein the floor interface surface includes a portion on each side of atibial eminence extending above the floor interface surface on thetibia. The method further includes performing a second set of cuts toprepare a tibial eminence wall interface surface, wherein the wallinterface surface extends substantially perpendicular to the floorinterface surface between the floor interface surface and a top surfaceof the tibial eminence. The method further includes performing a thirdset of cuts to prepare a radiused intersection between the floorinterface surface and the wall interface surface. The sets of cuts areperformed subject to a cutting restraint guide.

According to another embodiment, a surgical planning method forpreparing a tibia to receive a tibial implant component includesacquiring a representation of a proximal end of the tibia and acquiringa representation of a tibial implant. The planning method furtherincludes positioning the representation of the tibial implant on therepresentation of the proximal end of the tibia and planning preparationof the proximal end of the tibia based on the tibial implant. Theplanning preparation of the proximal end of the tibia includes planninga first set of cuts to prepare a floor interface surface on the tibia,wherein the floor interface surface comprises a portion on each side ofa tibial eminence extending above the floor interface portion on thetibia; planning a second set of cuts to prepare a tibial eminence wallinterface surface, wherein the wall interface surface extendssubstantially perpendicular to the floor interface between the floorinterface surface and a top surface of the tibial eminence; and planninga third set of cuts to prepare a radiused intersection between the floorinterface surface and the wall interface surface. The method furtherincludes providing a cutting restraint guide based on the plan of atleast one of the first, second, and third sets of cuts.

According to another embodiment, a surgical system includes a surgicaldevice configured to hold a surgical tool and be manipulated by a userto perform preparation of a tibia to receive an implant component, and acutting restraint guide configured to provide a constraint on movementof the surgical tool. The cutting restraint guide is configured to allowa user to perform a plurality of cuts including a first set of cuts toprepare a floor interface surface on the tibia, wherein the floorinterface surface comprises a portion on each side of a tibial eminenceextending above the floor interface portion on the tibia; a second setof cuts to prepare a tibial eminence wall interface surface, wherein thewall interface surface extends substantially perpendicular to the floorinterface between the floor interface surface and a top surface of thetibial eminence; and a third set of cuts to prepare a radiusedintersection between the floor interface surface and the wall interfacesurface.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are not restrictive of the invention, as claimed.

BRIEF DESCRIPTION OF THE FIGURES

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate several embodiments that,together with the description, serve to explain the principles andfeatures of the present disclosure.

FIG. 1 illustrates a perspective view of a post-operative prostheticknee joint fitted with a prosthetic system, consistent with an exemplaryembodiment.

FIG. 2 illustrates a top view of a proximal end of a tibia prepared toreceive a prosthetic component according to a traditional method.

FIG. 3 illustrates a top view of a proximal end of a tibia prepared toreceive a prosthetic component according to an exemplary embodiment.

FIG. 4 illustrates a perspective view of a proximal end of a tibiaprepared to receive a prosthetic component according to an exemplaryembodiment.

FIG. 5 illustrates a virtual representation of a haptic boundaryaccording to an exemplary embodiment.

FIG. 6 illustrates a method of preparing a proximal end of a tibia toreceive a prosthetic component according to an exemplary embodiment.

FIG. 7 illustrates a method of planning the preparation a proximal endof a tibia to receive a prosthetic component according to an exemplaryembodiment.

FIG. 8 illustrates a perspective view of an embodiment of a surgicalsystem according to an exemplary embodiment.

FIG. 9 illustrates a block diagram of a surgical system according to anexemplary embodiment.

DETAILED DESCRIPTION

Reference will now be made in detail to exemplary embodiments of thepresent disclosure, examples of which are illustrated in theaccompanying drawings.

A healthy knee joint comprises the interface between the distal end ofthe femur and the proximal end of the tibia. If the healthy knee jointbecomes damaged due, for example, to injury or disease, knee surgery maybe required to restore normal structure and function of the joint. Ifthe damage to the knee is severe, total knee arthroplasty (“TKA”) may berequired. TKA typically involves the removal of the damaged portion ofjoint and the replacement of the damaged portion of the joint with oneor more prosthetic components.

In some TKA procedures, one or more of cruciate ligaments (includinganterior cruciate ligament and/or posterior cruciate ligament) may beleft intact, to be re-used with the prosthetic implants to form the newknee joint. In these “cruciate-retaining” applications, the prostheticimplant components may be configured to avoid interference with orimpingement on the retained cruciate ligaments passing through theintercondylar area of the knee joint. For example, each of the femoraland tibial prosthetic components may be designed with a intercondylar“notch” that extends from the posterior of the prosthetic componenttoward the anterior of the prosthetic component. The femoral and tibialintercondylar notches overlap in the vertical direction, providing apassage that allows the cruciate ligament to pass from the femoralintercondylar fossa down to the tibial eminence.

Because cruciate ligaments are exposed to significant tensile forceduring normal knee joint use, it is important that the attachment siteswhere the cruciate ligaments attach to the femur and tibia havesufficient strength to properly anchor the cruciate ligaments to thebone. Otherwise, the force applied by the cruciate ligament strains thetissue around the attachment site, possibly leading to failure of thejoint, which may require corrective surgery to repair. One way to limitthe possibility of such a failure is to limit and carefully control theamount of bone resected at or near the attachment site(s) (i.e., theintercondylar fossa of the femur and tibial eminence 101 a of thetibia). Limiting the amount of disturbance of native tissue at theattachment sites helps preserve the natural anchoring mechanism of thetissue, which decreases the likelihood of failure at the attachmentsite.

In the embodiment illustrated in FIG. 1, prosthetic implant system 110includes a number of components configured to replace a resected portionof a native knee joint. According to one embodiment, prosthetic implantsystem 110 includes a tibial implant system 120 configured to replace aresected portion of a native tibia 101. Prosthetic implant system 110also includes a femoral component 130 configured to replace a resectedportion of a native femur 102. After implantation during kneereplacement surgery, tibial implant system 120 and femoral component 130cooperate to replicate the form and function of the native knee joint.

Femoral component 130 is secured to the distal end of femur 102 andconfigured to replace the structure and function of the native femoralportion of knee joint 100. As such, femoral component 130 may bemanufactured from surgical-grade metal or metal alloy material (such assurgical-grade steel, titanium or titanium allow, a cobalt-chromiumalloy, a zirconium alloy, or tantalum) that is substantially rigid forproviding sufficient strength to support the forces required of the kneejoint. According to one embodiment, femoral component 130 may embody asingle component having a plurality of different structural features,each configured to perform a particular function associated with theknee joint 100. For example, femoral component 130 may include a pair ofcondyles 132, each of which is coupled to a patellar guide portion 133.The pair of condyles 132 are separated from one another by anintercondylar notch 138, which provides a channel through which one ormore cruciate ligaments 103, such as anterior cruciate ligament (ACL)103 a and/or posterior cruciate ligament (PCL) 103 b, may pass.

Tibial implant system 120 may include a plurality of components thatcooperate to provide a stable surface that articulates with femoralcomponent 130 to restore proper knee joint function. As illustrated inFIG. 1, tibial implant system 120 includes a base portion 121 and one ormore insert portions 123. During a knee replacement procedure, baseportion 121 is secured to the proximal end of the tibia 101, which hasbeen surgically prepared by removing damaged bone and tissue andreshaping the healthy bone to receive the base portion 121. Once baseportion 121 is secured to tibia 101, the surgeon completes assembly oftibial implant system 120 by engaging and securing insert portions 123within base portion 121. Base portion 121 of tibial prosthetic systemmay be configured with a passage through the center to allow forconnection between the retained cruciate ligaments 103 and tibialeminence 101 a.

Base portion 121 may be configured to emulate the structure and functionof the top surface of tibia 101. Thus, similar to femoral component 130,base portion 121 may be manufactured from surgical-grade metal or metalalloy material (such as surgical-grade steel, titanium or titaniumallow, a cobalt-chromium alloy, a zirconium alloy, or tantalum) that issubstantially rigid for providing a stable base upon which toreconstruct the remainder of the prosthetic joint.

Insert portions 123 may be designed to emulate the form and function ofcertain components of the natural femorotibial interface, including,among other things, medial and lateral menisci of the knee joint. Assuch, insert portions 123 may be constructed of smooth, semi-rigidsynthetic or semi-synthetic plastic, rubber, or polymer material. Insertportions 123 may be configured to provide a smooth surface that isdesigned to articulate with a femoral component 130 during normal kneeoperation. According to one embodiment, insert portions 123 areconfigured to removably engage with base portion 121. Accordingly,insert portions 123 are configured for periodic replacement if insertportions 123 deteriorate over time due, for example, to excessive wear.

FIG. 2 depicts the proximal end of the tibia 101 prepared to receive atibial implant system, such as base portion 121 of tibial implant system120, prepared according to a traditional method. As shown, the preparedtibia 101 has a floor interface surface 151, having floor interfacesurface portions 151 a, 151 b on each side of tibial eminence 101 a. Thetibia 101 also has a wall interface surface 153 extending substantiallyperpendicular to floor interface surface 151 between the floor interfacesurface 151 and a top surface 102 of the tibial eminence 101 a.Preparation of the tibia as shown in FIG. 2, according to a traditionalmethod, uses a traditional saw, such as an oscillating sagittal saw orreciprocal saw, to make both the horizontal (to form the floor interfacesurface) and the vertical (to form the wall interface surface) cuts.Performing these two sets of cuts, in order to maintain a tibialeminence portion 101 a in the prepared bone, requires very controlleddelineation. Often, these cuts result in overcutting in either thehorizontal or vertical direction, and therefore compromising thestrength of the tibial eminence 101 a. In some practices of thistraditional method, drilled pins may be added at the intersectionbetween the floor interface surface 151 and the tibial eminence 101 a tostop overcutting and to help reduce stress risers. Nevertheless, sawblades tend to skive and can still overcut while making the horizontalor vertical cuts in the tibia 101. Furthermore, this additionaldisruption of the bone creates an additional violation of the bone.

Furthermore, as shown in FIG. 2, the use of the sagittal saw createssharp corners. For example, the intersection between the floor interfaceportion 151 and the wall interface portion 153, as well as theintersection between the wall interface portion 153 and the top surface102 of the tibial interface 101 a, form sharp edges which can lessencause stresses to the tibial eminence and reduce its overall strength.

FIGS. 3 and 4 depict the proximal end of the tibia 101 prepared toreceive a tibial implant system, such as base portion 121 of tibialimplant system 120, prepared according to the exemplary embodimentsdisclosed herein. As shown, the prepared tibia 101 has a floor interfacesurface 151, having floor interface surface portions 151 a, 151 b oneach side of tibial eminence 101 a. The tibia 101 also has a wallinterface surface 153 extending substantially perpendicular to floorinterface surface 151 between the floor interface surface 151 and a topsurface 102 of the tibial eminence 101 a. The tibia 101 also has abridge portion 154 between the floor interface surface portions 151 a,151 b at an anterior end of the tibial eminence 101 a. Finally, tibia101 has a curved or radiused intersection 152 between the floorinterface surface 151 and the wall interface surface 153.

Preparation of the tibia as shown in FIGS. 3 and 4 may be performedusing a number of different surgical cutting tools. As with thetraditional method, in a first set of cuts, the floor interface surface151 may be prepared using an oscillating surgical saw. In a second setof cuts, the wall interface surface 153 may also be prepared using asagittal saw or a reciprocal saw. As shown in FIGS. 3 and 4, accordingto an exemplary embodiment, a third set of cuts (which may be preparedin combination with the first or second set of cuts for preparing thefloor interface 151 surface or the wall interface surface 153,respectively) is prepared to form a radiused intersection 152 betweenthe floor interface surface 151 and the wall interface surface 153. Theradiused intersection 152 is preferably formed using a rotary cuttingtool such as a burr or rasp. The intersection 152 may be performed by arotary cutter having a large radius, wherein a single pass is needed tocreate the radiused intersection, or a tool having a smaller geometrymay be used to perform a sculpture milling technique to form theradiused intersection. In a preferred embodiment, the wall interfacesurface 153 is also prepared using a rotary cutter such as a burr orcylindrical rasp. In this way, both the intersection 152 and the topcorners between the wall interface surface 153 and the top surface 102of the tibial eminence 101 a are rounded. Also, other sharp edges andstress risers can be minimized through the use of the rotary cutter forthe wall interface surface 153, to include forming the radiusedintersection 152. In other embodiments, preparation of the floorinterface surface 151 may also be performed using a rotary cutting tool,such as a burr or cylindrical rasp. As such, any of the first, second,or third sets of cuts may be performed using a rotary cutter, inaccordance with the present disclosure. The anterior bridge 154 may bepunched or rongeured. In a preferred embodiment, the anterior bridge 154is also formed using a rotary cutter.

The tibia 101 depicted in FIGS. 3 and 4 also has prepared therein pegapertures 157, which may be drilled or burred using the rotary cutterinto the floor interface surface 151. The peg apertures 157 areconfigured to receive elongated projections from the tibial implantsystem 120, to further secure the implant to the bone, and resistmovement between the implant and the bone. Similarly, the bone may beprepared with keels (not shown) which interface with keels on the tibialimplant system 120, and which also improve the security between the boneand the implant.

Methods of preparing the tibia to receive a tibial implant system alsoinclude utilizing precise cutting boundaries so as to limit the amountof overcutting that can compromise the strength of the tibial eminence101 a. FIG. 5 depicts one embodiment of a cutting restraint guide usedin the exemplary methods of this disclosure. The figure showsimplementation of a haptic boundary 501, provided in conjunction with asurgical system (described in greater detail below), to control the cutsmade during preparation of the bone. A surgical system, such as system200 depicted in FIG. 8, may be configured to establish a virtual hapticgeometry associated with the planned prosthetic implant component andassociated with or relative to one or more features of a patient'sanatomy. The surgical system 200 may be configured to create a virtualrepresentation of a surgical site that includes, for example, virtualrepresentations of a patient's anatomy, a surgical instrument to be usedduring a surgical procedure, a probe tool for registering other objectswithin the surgical site, and any other such object associated with asurgical site.

In addition to physical objects, surgical system 200 may be configuredto generate virtual objects that exist in software and may be usefulduring the performance of a surgical procedure. For example, surgicalsystem 200 may be configured to generate virtual boundaries, such ashaptic boundary 501, that correspond to a surgeon's plan for preparing abone, such as boundaries defining areas of the bone that the surgeonplans to cut, remove, or otherwise alter. Alternatively or additionally,surgical system 200 may define virtual objects that correspond to adesired path or course over which a portion of surgical tool 210 shouldnavigate to perform a particular task.

Virtual boundaries and other virtual objects may define a point, line,or surface within a virtual coordinate space (typically defined relativeto an anatomy of a patient) that serves as a boundary at which hapticfeedback is provided to a surgical instrument when the tracked positionof the surgical instrument interacts with the virtual boundary orobject. For example, as the surgeon performs a bone cutting operation, atracking system of the surgical system 200 tracks the location of thecutting tool and, in most cases, allows the surgeon to freely move thetool in the workspace. However, when the tool is in proximity to avirtual haptic boundary (that has been registered to the anatomy of thepatient), surgical system 200 controls the force feedback system toprovide haptic guidance that tends to constrain the surgeon frompenetrating the virtual haptic boundary with the cutting tool. Forexample, a virtual haptic boundary may be associated with the geometryof a virtual model of a prosthetic implant, and the haptic guidance maycomprise a force and/or torque that is mapped to the virtual boundaryand experienced by the surgeon as resistance to constrain tool movementfrom penetrating the virtual boundary. Thus, the surgeon may feel as ifthe cutting tool has encountered a physical object, such as a wall.Accordingly, the force feedback system of the surgical system 200communicates information to the surgeon regarding the location of thetool relative to the virtual boundary, and provides physical forcefeedback to guide the cutting tool during the actual cutting process. Inthis manner, the virtual boundary functions as a virtual cutting guide.The force feedback system of the surgical system 200 may also beconfigured to limit the user's ability to manipulate the surgical tool.

As shown in FIG. 5, exemplary haptic boundary 501 is generated to allowmanipulation of a surgical tool in the working area 502. The hapticboundary 501 is positioned around the desired tibial eminence area 101a. In this way, the surgeon is able to make cuts to the tibia 101 tocreate the floor interface surface 151 and anterior bridge portion 154,without overcutting to compromise the strength of the tibial eminence101 a. As shown, haptic boundary 501 is created at a desired offset fromthe planned tibial eminence 101 a so as to keep the tool from cuttingtoo closely. The haptic boundary 501 may be automatically generatedbased on the tibial implant system to be used and may also be customizedby the surgeon. For example, the surgeon may want to increase ordecrease the size of the haptic boundary 501, may want to change theboundary offset from the planned tibial eminence 101 a, or may want toreposition the planned implant system on the patient's anatomy, andtherefore reposition the haptic boundary 501. The surgical system 200may be configured to allow these inputs by the surgeon through a userinterface. Additional haptic boundaries may be generated and applied tothe surgical tool for the other sets of cuts, such as for cutting thewall interface surface, to complete the bone preparation according tothe disclosed embodiments.

The use of the haptic boundaries generated and applied through asurgical system is one mechanism for creating a cutting restraint guidefor performing the present methods. Other embodiments of the cuttingrestraint guide include a mechanical restraint that may be applied tothe cutting tool or to an arm holding the cutting tool, or may becutting blocks that are created specific to the surgical plan to allow asurgeon to manipulate the tools according to the surgical plan.

Preparation of the joint as described above may be performed accordingto an exemplary embodiment depicted in FIG. 6. A method of preparing thebone includes performing a first set of cuts to prepare a floorinterface surface 151 on the tibia (step 601). The floor interfacesurface 151 includes a portion 151 a, 151 b on each side of a tibialeminence 101 a, extending above the floor interface surface 151 on thetibia 101. The method further includes performing a second set of cutsto prepare a tibial eminence wall interface surface 153 (step 602). Thewall interface surface 153 extends substantially perpendicular to thefloor interface surface 151 between the floor interface surface 151 anda top surface 102 of the tibial eminence 101 a. The method furtherincludes performing a third set of cuts to prepare a radiusedintersection between the floor interface surface and the wall interfacesurface (step 603). As discussed above, the sets of cuts are performedsubject to a cutting restraint guide. In other embodiments, steps 601,602, and 603 may be performed in a different order from that shown inFIG. 6. Similarly, the third set of cuts (step 603) can be performed inconjunction with step 601 or step 602 when those steps involve cuttingusing a rotary cutter. As mentioned above, one or more of the sets ofcuts may be performed using a rotary cutter.

Planning for preparation of the joint as described above may beperformed according to an exemplary embodiment depicted in FIG. 7. Thesurgical planning method includes acquiring a representation of aproximal end of the tibia (step 701). The representation of the anatomymay be acquired by an imaging system and may include images such as CTor MRI images. The images may be acquired pre-operatively,intraoperatively, or at the time of surgical planning. The images may beloaded and acquired through surgical system 200, described below. Themethod also includes acquiring a representation of a tibial implant(step 702). Model implants may also be loaded and acquired throughsurgical system 200. The surgeon may be able to select from a number ofdifferent implant models and choose the implant that is most appropriatefor the patient and the patient's anatomy. The planning method furtherincludes positioning the representation of the tibial implant on therepresentation of the proximal end of the tibia and planning preparationof the proximal end of the tibia based on the tibial implant (step 703).The surgeon may be able to modify the position of the implant on theanatomy of the patient. Positioning of the model implant on therepresentation on the bone allows for planning the resections necessaryto prepare the bone to receive the tibial implant, including planning afirst set of cuts to prepare a floor interface surface 151 on the tibia101 (step 704). The floor interface surface 151 comprises a portion 151a, 151 b on each side of a tibial eminence 101 a extending above thefloor interface portion on the tibia. Step 705 includes planning asecond set of cuts to prepare a tibial eminence wall interface surface153. The wall interface surface 153 extends substantially perpendicularto the floor interface surface 151 between the floor interface surface151 and a top surface 102 of the tibial eminence 101 a. Step 706includes planning a third set of cuts to prepare a radiused intersection152 between the floor interface surface 151 and the wall interfacesurface 153. The method further includes providing a cutting restraintguide based on the plan of at least one of the first, second, and thirdsets of cuts (step 707).

An exemplary approach to ensure precise and accurate preparation of thejoint according to the methods of the exemplary embodiments describedabove may utilize a computer-assisted surgery (CAS) system to aid thesurgeon in properly aligning the tool prior to interaction withpatient's anatomy and performing accurate cuts in the bone. Many CASsystems include software that allow users to electronically registercertain anatomic features (e.g., bones, soft tissues, etc.), surgicalinstruments, and other landmarks associated with the surgical site. CASsystems may generate a graphical representation of the surgical sitebased on the registration of the anatomic features. The CAS softwarealso allows users to plan certain aspects of the surgical procedure, andregister these aspects for display with the graphical representation ofthe surgical site. For example, in a knee joint replacement procedure, asurgeon may register target navigation points, the location and depth ofbone and tissue cuts, virtual boundaries that may be associated with acorresponding reference for the application of haptic force, and otheraspects of the surgery.

FIG. 8 provides a schematic diagram of an exemplary computer-assistedsurgery (CAS) system 200, in which processes and features associatedwith certain disclosed embodiments may be implemented. Surgical system200 may be configured to perform a wide variety of orthopedic surgicalprocedures such as, for example, partial or total joint replacementsurgeries. As illustrated in FIG. 2, surgical system 200 includes atracking system 201, computing system 202, one or more display devices203 a, 203 b, and a robotic system 204. It should be appreciated thatsystem 200, as well as the methods and processes described herein, maybe applicable to many different types of joint replacement procedures.Although certain disclosed embodiments may be described with respect toknee replacement procedures, the concepts and methods described hereinmay be applicable to other types of orthopedic surgeries, such aspartial hip replacement, full or partial hip resurfacing, shoulderreplacement or resurfacing procedures, and other types of orthopedicprocedures.

Robotic system 204 can be used in an interactive manner by a surgeon toperform a surgical procedure, such as a knee replacement procedure, on apatient. As shown in FIG. 2, robotic system 204 includes a base 205, anarticulated arm 206, a force system (not shown), and a controller (notshown). A surgical tool 210 (e.g., an end effector having an operatingmember, such as a saw, reamer, or burr) may be coupled to thearticulated arm 206. The surgeon can manipulate the surgical tool 210 bygrasping and manually moving the articulated arm 206 and/or the surgicaltool 210.

The force system and controller are configured to provide the cuttingrestraint guide via control or guidance to the surgeon duringmanipulation of the surgical tool. The force system is configured toprovide at least some force to the surgical tool via the articulated arm206, and the controller is programmed to generate control signals forcontrolling the force system. In one embodiment, the force systemincludes actuators and a back-driveable transmission that provide haptic(or force) feedback to constrain or inhibit the surgeon from manuallymoving the surgical tool beyond predefined haptic boundaries defined byhaptic objects as described, for example, in U.S. Pat. No. 8,010,180and/or U.S. patent application Ser. No. 12/654,519 (U.S. PatentApplication Pub. No. 2010/0170362), filed Dec. 22, 2009, each of whichis hereby incorporated by reference herein in its entirety. According toone embodiment, surgical system 200 is the RIO® Robotic Arm InteractiveOrthopedic System manufactured by MAKO Surgical Corp. of FortLauderdale, Fla. The force system and controller may be housed withinthe robotic system 204.

Tracking system 201 is configured to determine a pose (i.e., positionand orientation) of one or more objects during a surgical procedure todetect movement of the object(s). For example, the tracking system 201may include a detection device that obtains a pose of an object withrespect to a coordinate frame of reference of the detection device. Asthe object moves in the coordinate frame of reference, the detectiondevice tracks the pose of the object to detect (or enable the surgicalsystem 200 to determine) movement of the object. As a result, thecomputing system 202 can capture data in response to movement of thetracked object or objects. Tracked objects may include, for example,tools/instruments, patient anatomy, implants/prosthetic devices, andcomponents of the surgical system 200. Using pose data from the trackingsystem 201, the surgical system 200 is also able to register (or map orassociate) coordinates in one space to those in another to achievespatial alignment or correspondence (e.g., using a coordinatetransformation process as is well known). Objects in physical space maybe registered to any suitable coordinate system, such as a coordinatesystem being used by a process running on the surgical controller 212and/or the computer device of the haptic device 204. For example,utilizing pose data from the tracking system 201, the surgical system200 is able to associate the physical anatomy, such as the patient'stibia, with a representation of the anatomy (such as an image displayedon the display device 203). Based on tracked object and registrationdata, the surgical system 200 may determine, for example, a spatialrelationship between the image of the anatomy and the relevant anatomy.

Registration may include any known registration technique, such as, forexample, image-to-image registration (e.g., monomodal registration whereimages of the same type or modality, such as fluoroscopic images or MRimages, are registered and/or multimodal registration where images ofdifferent types or modalities, such as MRI and CT, are registered);image-to-physical space registration (e.g., image-to-patientregistration where a digital data set of a patient's anatomy obtained byconventional imaging techniques is registered with the patient's actualanatomy); and/or combined image-to-image and image-to-physical-spaceregistration (e.g., registration of preoperative CT and MM images to anintraoperative scene). The computing system 202 may also include acoordinate transform process for mapping (or transforming) coordinatesin one space to those in another to achieve spatial alignment orcorrespondence. For example, the surgical system 200 may use thecoordinate transform process to map positions of tracked objects (e.g.,patient anatomy, etc.) into a coordinate system used by a processrunning on the computer of the haptic device and/or the surgicalcontroller 212. As is well known, the coordinate transform process mayinclude any suitable transformation technique, such as, for example,rigid-body transformation, non-rigid transformation, affinetransformation, and the like.

The tracking system 201 may be any tracking system that enables thesurgical system 200 to continually determine (or track) a pose of therelevant anatomy of the patient. For example, the tracking system 201may include a non-mechanical tracking system, a mechanical trackingsystem, or any combination of non-mechanical and mechanical trackingsystems suitable for use in a surgical environment. The non-mechanicaltracking system may include an optical (or visual), magnetic, radio, oracoustic tracking system. Such systems typically include a detectiondevice adapted to locate in predefined coordinate space speciallyrecognizable trackable elements (or trackers) that are detectable by thedetection device and that are either configured to be attached to theobject to be tracked or are an inherent part of the object to betracked. For example, a trackable element may include an array ofmarkers having a unique geometric arrangement and a known geometricrelationship to the tracked object when the trackable element isattached to the tracked object. The known geometric relationship may be,for example, a predefined geometric relationship between the trackableelement and an endpoint and axis of the tracked object. Thus, thedetection device can recognize a particular tracked object, at least inpart, from the geometry of the markers (if unique), an orientation ofthe axis, and a location of the endpoint within a frame of referencededuced from positions of the markers.

The markers may include any known marker, such as, for example,extrinsic markers (or fiducials) and/or intrinsic features of thetracked object. Extrinsic markers are artificial objects that areattached to the patient (e.g., markers affixed to skin, markersimplanted in bone, stereotactic frames, etc.) and are designed to bevisible to and accurately detectable by the detection device. Intrinsicfeatures are salient and accurately locatable portions of the trackedobject that are sufficiently defined and identifiable to function asrecognizable markers (e.g., landmarks, outlines of anatomical structure,shapes, colors, or any other sufficiently recognizable visualindicator). The markers may be located using any suitable detectionmethod, such as, for example, optical, electromagnetic, radio, oracoustic methods as are well known. For example, an optical trackingsystem having a stationary stereo camera pair sensitive to infraredradiation may be used to track markers that emit infrared radiationeither actively (such as a light emitting diode or LED) or passively(such as a spherical marker with a surface that reflects infraredradiation). Similarly, a magnetic tracking system may include astationary field generator that emits a spatially varying magnetic fieldsensed by small coils integrated into the tracked object.

Computing system 202 may be communicatively coupled to tracking system201 and may be configured to receive tracking data from tracking system201. Based on the received tracking data, computing system 202 maydetermine the position and orientation associated with one or moreregistered features of the surgical environment, such as surgical tool210 or portions of the patient's anatomy. Computing system 202 may alsoinclude surgical planning and surgical assistance software that may beused by a surgeon or surgical support staff during the surgicalprocedure. For example, during a joint replacement procedure, computingsystem 202 may display images related to the surgical procedure on oneor both of the display devices 203 a, 203 b.

Computing system 202 (and/or one or more constituent components ofsurgical system 200) may include hardware and software for operation andcontrol of the surgical system 200. Such hardware and/or software isconfigured to enable the system 200 to perform the techniques describedherein. Referring to FIG. 9, the computing system 202 includes asurgical controller 212, a display device 203, and an input device 216.

The surgical controller 212 may be any known computing system but ispreferably a programmable, processor-based system. For example, thesurgical controller 212 may include a microprocessor, a hard drive,random access memory (RAM), read only memory (ROM), input/output (I/O)circuitry, and any other known computer component. The surgicalcontroller 212 is preferably adapted for use with various types ofstorage devices (persistent and removable), such as, for example, aportable drive, magnetic storage, solid state storage (e.g., a flashmemory card), optical storage, and/or network/Internet storage. Thesurgical controller 212 may comprise one or more computers, including,for example, a personal computer or a workstation operating under asuitable operating system and preferably includes a graphical userinterface (GUI).

Referring again to FIG. 9, in an exemplary embodiment, the surgicalcontroller 212 includes a processing circuit 220 having a processor 222and memory 224. Processor 222 can be implemented as a general purposeprocessor executing one or more computer programs to perform actions byoperating on input data and generating output. The processes and logicflows can also be performed by, and apparatus can also be implementedas, special purpose logic circuitry, e.g., an FPGA (field programmablegate array) or an ASIC (application specific integrated circuit), agroup of processing components, or other suitable electronic processingcomponents. Generally, a processor will receive instructions and datafrom a read only memory or a random access memory or both. Memory 224(e.g., memory, memory unit, storage device, etc.) comprises one or moredevices (e.g., RAM, ROM, Flash-memory, hard disk storage, etc.) forstoring data and/or computer code for completing or facilitating thevarious processes described in the present application. Memory 224 maybe or include volatile memory or non-volatile memory. Memory 224 mayinclude database components, object code components, script components,or any other type of information structure for supporting the variousactivities described in the present application. According to anexemplary embodiment, memory 224 is communicably connected to processor222 and includes computer code for executing one or more processesdescribed herein. The memory 224 may contain a variety of modules, eachcapable of storing data and/or computer code related to specific typesof functions. In one embodiment, memory 224 contains several modulesrelated to surgical procedures, such as a planning module 224 a, anavigation module 224 b, a registration module 224 c, and a roboticcontrol module 224 d.

Alternatively or in addition, the program instructions can be encoded onan artificially generated propagated signal, e.g., a machine-generatedelectrical, optical, or electromagnetic signal, that is generated toencode information for transmission to suitable receiver apparatus forexecution by a data processing apparatus. A computer storage medium canbe, or be included in, a computer-readable storage device, acomputer-readable storage substrate, a random or serial access memoryarray or device, or a combination of one or more of them. Moreover,while a computer storage medium is not a propagated signal, a computerstorage medium can be a source or destination of computer programinstructions encoded in an artificially generated propagated signal. Thecomputer storage medium can also be, or be included in, one or moreseparate components or media (e.g., multiple CDs, disks, or otherstorage devices). Accordingly, the computer storage medium may betangible and non-transitory.

A computer program (also known as a program, software, softwareapplication, script, or code) can be written in any form of programminglanguage, including compiled or interpreted languages, declarative orprocedural languages, and it can be deployed in any form, including as astand-alone program or as a module, component, subroutine, object, orother unit suitable for use in a computing environment. A computerprogram may, but need not, correspond to a file in a file system. Aprogram can be stored in a portion of a file that holds other programsor data (e.g., one or more scripts stored in a markup languagedocument), in a single file dedicated to the program in question, or inmultiple coordinated files (e.g., files that store one or more modules,sub programs, or portions of code). A computer program can be deployedto be executed on one computer or on multiple computers that are locatedat one site or distributed across multiple sites and interconnected by acommunication network.

Generally, a computer will also include, or be operatively coupled toreceive data from or transfer data to, or both, one or more mass storagedevices for storing data, e.g., magnetic, magneto optical disks, oroptical disks. However, a computer need not have such devices. Moreover,a computer can be embedded in another device, e.g., a mobile telephone,a personal digital assistant (PDA), a mobile audio or video player, agame console, a Global Positioning System (GPS) receiver, or a portablestorage device (e.g., a universal serial bus (USB) flash drive), to namejust a few. Devices suitable for storing computer program instructionsand data include all forms of non-volatile memory, media and memorydevices, including by way of example semiconductor memory devices, e.g.,EPROM, EEPROM, and flash memory devices; magnetic disks, e.g., internalhard disks or removable disks; magneto optical disks; and CD ROM andDVD-ROM disks. The processor and the memory can be supplemented by, orincorporated in, special purpose logic circuitry.

Embodiments of the subject matter described in this specification can beimplemented in a computing system that includes a back end component,e.g., as a data server, or that includes a middleware component, e.g.,an application server, or that includes a front end component, e.g., aclient computer having a graphical user interface or a Web browserthrough which a user can interact with an embodiment of the subjectmatter described in this specification, or any combination of one ormore such back end, middleware, or front end components. The componentsof the system can be interconnected by any form or medium of digitaldata communication, e.g., a communication network. Examples ofcommunication networks include a local area network (“LAN”) and a widearea network (“WAN”), an inter-network (e.g., the Internet), andpeer-to-peer networks (e.g., ad hoc peer-to-peer networks).

Referring to the embodiment of surgical system 200 depicted in FIG. 9,the surgical controller 212 further includes a communication interface230. The communication interface 230 of the computing system 202 iscoupled to a computing device (not shown) of the robotic system 204 viaan interface and to the tracking system 201 via an interface. Theinterfaces can include a physical interface and a software interface.The physical interface of the communication interface 230 can be orinclude wired or wireless interfaces (e.g., jacks, antennas,transmitters, receivers, transceivers, wire terminals, etc.) forconducting data communications with external sources via a directconnection or a network connection (e.g., an Internet connection, a LAN,WAN, or WLAN connection, etc.). The software interface may be residenton the surgical controller 212, the computing device (not shown) of therobotic system 204, and/or the tracking system 201. In some embodiments,the surgical controller 212 and the computing device (not shown) are thesame computing device. The software may also operate on a remote server,housed in the same building as the surgical system 200, or at anexternal server site.

Computing system 202 also includes display device 203. The displaydevice 203 is a visual interface between the computing system 52 and theuser. The display device 203 is connected to the surgical controller 212and may be any device suitable for displaying text, images, graphics,and/or other visual output. For example, the display device 203 mayinclude a standard display screen (e.g., LCD, CRT, OLED, TFT, plasma,etc.), a touch screen, a wearable display (e.g., eyewear such as glassesor goggles), a projection display, a head-mounted display, a holographicdisplay, and/or any other visual output device. The display device 203may be disposed on or near the surgical controller 212 (e.g., on thecart as shown in FIG. 8) or may be remote from the surgical controller212 (e.g., mounted on a stand with the tracking system 56). The displaydevice 203 is preferably adjustable so that the user canposition/reposition the display device 203 as needed during a surgicalprocedure. For example, the display device 203 may be disposed on anadjustable arm (not shown) or to any other location well-suited for easeof viewing by the user. As shown in FIG. 8 there may be more than onedisplay device 203 in the surgical system 200.

The display device 203 may be used to display any information useful fora medical procedure, such as, for example, images of anatomy generatedfrom an image data set obtained using conventional imaging techniques,graphical models (e.g., CAD models of implants, instruments, anatomy,etc.), graphical representations of a tracked object (e.g., anatomy,tools, implants, etc.), constraint data (e.g., axes, articular surfaces,etc.), representations of implant components, digital or video images,registration information, calibration information, patient data, userdata, measurement data, software menus, selection buttons, statusinformation, and the like.

In addition to the display device 203, the computing system 202 mayinclude an acoustic device (not shown) for providing audible feedback tothe user. The acoustic device is connected to the surgical controller212 and may be any known device for producing sound. For example, theacoustic device may comprise speakers and a sound card, a motherboardwith integrated audio support, and/or an external sound controller. Inoperation, the acoustic device may be adapted to convey information tothe user. For example, the surgical controller 212 may be programmed tosignal the acoustic device to produce a sound, such as a voicesynthesized verbal indication “DONE,” to indicate that a step of asurgical procedure is complete. Similarly, the acoustic device may beused to alert the user to a sensitive condition, such as producing atone to indicate that a surgical cutting tool is nearing a criticalportion of soft tissue or is approaching the haptic boundary.

To provide for other interaction with a user, embodiments of the subjectmatter described in this specification can be implemented on a computerhaving input device 216 that enables the user to communicate with thesurgical system 200. The input device 216 is connected to the surgicalcontroller 212 and may include any device enabling a user to provideinput to a computer. For example, the input device 216 can be a knowninput device, such as a keyboard, a mouse, a trackball, a touch screen,a touch pad, voice recognition hardware, dials, switches, buttons, atrackable probe, a foot pedal, a remote control device, a scanner, acamera, a microphone, and/or a joystick. For example, input device 216can allow the user manipulate the haptic boundary as discussed above.Other kinds of devices can be used to provide for interaction with auser as well; for example, feedback provided to the user can be any formof sensory feedback, e.g., visual feedback, auditory feedback, ortactile feedback; and input from the user can be received in any form,including acoustic, speech, or tactile input. In addition, a computercan interact with a user by sending documents to and receiving documentsfrom a device that is used by the user; for example, by sending webpages to a web browser on a user's client device in response to requestsreceived from the web browser.

General surgical planning and navigation to carry out the exemplarymethods described above, and including haptic control and feedback asdescribed in connection with surgical system 200, may be performed by acomputerized surgical system such as that described in U.S. Pat. No.8,010,180 “Haptic Guidance System and Method” to Quaid et al., which isincorporated herein by reference in its entirety.

The construction and arrangement of the systems and methods as shown inthe various exemplary embodiments are illustrative only. Although only afew embodiments have been described in detail in this disclosure, manymodifications are possible. Accordingly, all such modifications areintended to be included within the scope of the present disclosure. Theorder or sequence of any process or method steps may be varied orre-sequenced according to alternative embodiments. Other substitutions,modifications, changes, and omissions may be made in the design,operating conditions and arrangement of the exemplary embodimentswithout departing from the scope of the present disclosure.

What is claimed is:
 1. A surgical system, comprising: an end effectorconfigured to facilitate preparation of a bone to receive an implantcomponent, the preparation of the bone comprising creating a radiusedintersection between a first planar surface and a second planar surfaceextending at an angle relative to the first planar surface; a feedbackmechanism coupled to the end effector; a computing system programmed to:define one or more virtual objects which define one or more positions ofthe end effector relative to the bone suitable for creation of theradiused intersection: control the feedback mechanism using the one ormore virtual objects to provide a constraint on manual movement of theend effector relative to the bone to facilitate creation of the radiusedintersection.
 2. The surgical system of claim 1, wherein the endeffector is a cutting tool.
 3. The surgical system of claim 1, whereinthe end effector is a burr.
 4. The surgical system of claim 1, thesurgical system further comprising a tracking system configured todetermine a location of the bone relative to a location of the endeffector.
 5. The surgical system of claim 1, wherein the first planarsurface comprises a floor interface surface on the tibia, wherein thefloor interface surface comprises a portion on each side of a tibialeminence extending above the floor interface surface on the tibia. 6.The surgical system of claim 5, wherein the second planar surfacecomprises a tibial eminence wall interface surface, wherein the wallinterface surface extends substantially perpendicular to the floorinterface between the floor interface surface and a top surface of thetibial eminence.
 7. A surgical system, comprising: a first cutting toolconfigured to be manipulated by a user to perform a first portion of apreparation of a bone to receive an implant component, the first portionof the preparation providing the bone with: a first planar surface; anda second planar surface, wherein the second planar surface extends at anangle relative to the first planar surface; and a rotary cutting toolconfigured to be manipulated by a user to perform a second portion ofthe preparation of the bone, the second portion of the preparationproviding the bone with a radiused intersection between the first planarsurface and the second planar surface; a feedback mechanism coupleableto the rotary cutting tool; and a computing system programmed to:generate a virtual object defining a cutting boundary corresponding toat least the radiused intersection; associate the virtual object withthe bone; and control the feedback mechanism to provide a constraint onmovement of the rotary cutting tool based on the virtual object, theconstraint configured to ensure accurate preparation of at least theradiused intersection.
 8. The system of claim 7, wherein the rotarycutting tool is a burr.
 9. The system of claim 7, wherein the firstcutting tool is a reciprocating saw.
 10. The system of claim 7, whereinthe feedback mechanism provides a haptic force applied to the rotarycutting tool to constrain the rotary cutting tool to the cuttingboundary.
 11. The system of claim 7, further comprising a mechanicalcutting guide configured for guiding the first cutting tool.
 12. Thesystem of claim 7, wherein the bone is a tibia.
 13. The system of claim12, wherein the first planar surface comprises a floor interface surfaceon the tibia, wherein the floor interface surface comprises a portion oneach side of a tibial eminence extending above the floor interfacesurface on the tibia.
 14. The system of claim 13, wherein the secondplanar surface comprises a tibial eminence wall interface surface,wherein the wall interface surface extends substantially perpendicularto the floor interface between the floor interface surface and a topsurface of the tibial eminence.
 15. The system of claim 7, comprising atracking system configured to track a position of the bone.